My girl got the same problem when she was 1.5mths, with “佢鼻仔入面有好多鼻涕咁既聲” but no fever at all. My problem even worse as it carried on for few weeks and she became difficult to BF. At the end, the doctor prescribed some cold medicine to stop the 鼻涕 first, then cough syrup to stop cough and melt the spam. It takes another week to recover after she took the medicine. My experience is that it’s very difficult to recover by themselves or it will cause them a long time of discomfort, esp. nasal conjestion which will hinder them from good feeding. Also, I strongly recommend u to keep the room always at 25-26C and moist so they recover faster.